Proton exchange membrane fuel cells(PEMFCs)are largely used in various applications because of their pollution-free products and high energy conversion efficiency.In order to improve the related design,in the present ...Proton exchange membrane fuel cells(PEMFCs)are largely used in various applications because of their pollution-free products and high energy conversion efficiency.In order to improve the related design,in the present work a new spiral flow field with a bypass is proposed.The reaction gas enters the flow field in the central path and diffuses in two directions through the flow channel and the bypass.The bypasses are arranged incrementally.The number of bypasses and the cross-section size of the bypasses are varied parametrically while a single-cell model of the PEMFC is used.The influence of the concentration of liquid water and oxygen in the cell on the performance of different flow fields is determined by means of Computational fluid dynamics(COMSOL Multiphysics software).Results show that when the bypass number is 48 and its cross-sectional area is 0.5 mm^(2),the cell exhibits the best performances.展开更多
Two full 3D steady mathematical models are developed by finite element method (FEM) to calcalate coupled physics fields. the electro-magnetic model is built and solved first and so is the fluid motion model with the...Two full 3D steady mathematical models are developed by finite element method (FEM) to calcalate coupled physics fields. the electro-magnetic model is built and solved first and so is the fluid motion model with the acquired electromagnetic force as source body forces in Navier-Stokes equations. Effects caused by the ferromagnetic shell, busbar system around, and open boundary problem as well as inside induced current were considered in terms of the magnetic field. Furthermore, a new modeling method is found to set up solid models and then mesh them entirely with so-called structuralized grids, namely hex-mesh. Examples of 75kA prebaked cell with two kinds of busbar arrangements are presented. Results agree with those disclosed in the literature and confirm that the coupled simulation is valid. It is also concluded that the usage of these models facilitates the consistent analysis of the electric field to magnetic field and then flow motion to the greater extent, local distributions of current density and magnetic flux density are very much dependent on the cell structure, the steel shell is a shield to reduce the magnetic field and flow pattern is two dimensional in the main body of the metal pad.展开更多
A simulation method for slug flow based on the VOF multiphase flow model was implemented in ANSYS?Fluent via a user-defined function(UDF)and applied to the dissipation of liquid slugs in the inlet pipe of a gas–liqui...A simulation method for slug flow based on the VOF multiphase flow model was implemented in ANSYS?Fluent via a user-defined function(UDF)and applied to the dissipation of liquid slugs in the inlet pipe of a gas–liquid cylindrical cyclone(GLCC)separator while varying the expanding diameter ratio and angle of inclination.The dissipation of liquid slug in inlet pipe is analyzed under different expanding diameter ratios and inclination angles.In the inlet pipe,it is found that increasing expanding diameter ratio and inclination angle can reduce the liquid slug stability and enhancing the effect of gravity,which is beneficial to slug flow dissipation.In the cylinder,increasing the expanding diameter ratio can significantly reduce the liquid carrying depth of the gas phase but result in a slightly increase of the gas content in the liquid phase space.Moreover,increasing the inclination angle results in a decrease in the carrying depth of liquid in the vapor phase,but enhances gas–liquid mixing and increases the gas-carrying depth in the liquid phase.Taking into consideration the dual effects of slug dissipation in the inlet pipe and carrying capacity of gas/liquid spaces in the cylinder,the optimal expanding diameter ratio and inclination angle values can be determined.展开更多
In order to explore the internal wind field flow characteristics of T4-72 type centrifugal fan, the three-dimensional model was established based on PRO/E software. Combined with computational fluid Dynamics Software ...In order to explore the internal wind field flow characteristics of T4-72 type centrifugal fan, the three-dimensional model was established based on PRO/E software. Combined with computational fluid Dynamics Software Fluent 6.3, the standard model and SIMPLEC algorithm were used to simulate the wind field inside the fan. Analysis of the flow characteristics, velocity distributed and pressure distributed of the internal fluid model of the T4-72 centrifugal fan, combined with the theoretical formula to obtain the full pressure, power and efficiency performance parameters of the fan. The centrifugal fan performance curve is drawn. While compared with the experimental data, it is found that the internal flow disturbance is strong when the fan is running under low load condition and high load condition, which affects the performance of the fan and reduces the life of the fan. The numerical simulation results are consistent with the experimental results. The overall performance parameters of the fan are in good agreement, verifying the reliability of the simulation results;when the fan works between 1 - 1.4 times the rated flow rate, it can obtain a more stable flow field while maintaining higher efficiency, which provides a new idea for the optimization of the subsequent fan.展开更多
To get fiber motion in condensing zone of compact spinning,velocity of this area is achieved by simulation,and then a bead-elastic rod fiber model is established.Based on simulation and dynamic analysis on this zone,g...To get fiber motion in condensing zone of compact spinning,velocity of this area is achieved by simulation,and then a bead-elastic rod fiber model is established.Based on simulation and dynamic analysis on this zone,governing equations are constructed and Runge-Kutta approach is used.Lastly,trajectories of fibers are calculated by specially designed Matlab procedure according to the principles mentioned above.Results show that fiber motions at different initial positions are different;X-axis velocity component makes fibers gathering on sides of suction slot;Y-axis airflow gets fibers gradually close and then stick to the surface of lattice apron.Fiber motions also reflect that the compact spinning process in condensing zone can be divided into three parts:fast convergence zone,adjustment convergence zone,and steady convergence zone.展开更多
In order to solve the problem of using middle or low water pressure to form fine water mist,a new nozzle is proposed in fire rescue robot.Existing water mist nozzles are basically used for high pressure and in large s...In order to solve the problem of using middle or low water pressure to form fine water mist,a new nozzle is proposed in fire rescue robot.Existing water mist nozzles are basically used for high pressure and in large size,complex structure and poor low pressure atomization effect in comparison with requirement of snake-like fire rescue robots.On the basis of comprehensive typical spray nozzles,a direct spiral double helix converging nozzle(DSDHCN) is proposed,which has the advantages of small volume,light weight,simple structure,and convenient installation.To make the spray nozzle have good performance,and meet the requirements of more efficient fire extinguishing,a numerical study is carried out to analyze the internal and external full flow field of nozzle.A gas-liquid two-phase flow is applied to simulate the external full flow field of nozzle with VOF model in fluent software.The simulation results show the real situation of water flow out of the atomization nozzle and the water jet trajectory.Some simulations about middle or low water pressure direct spiral double helix converging optimized nozzle have been done in 30 bar pressure.The simulation results show that the optimized nozzle structure not only makes the spray droplets have a good cone angle,but also have a sufficient axial velocity,which proves the structure rationality of the proposed optimized nozzle.展开更多
The control rod drive mechanism(CRDM)is an essential part of the control and safety protection system of pressurized water reactors.Current CRDM simulations are mostly performed collectively using a single method,igno...The control rod drive mechanism(CRDM)is an essential part of the control and safety protection system of pressurized water reactors.Current CRDM simulations are mostly performed collectively using a single method,ignoring the influence of multiple motion units and the differences in various features among them,which strongly affect the efficiency and accuracy of the simulations.In this study,we constructed a flow field fusion simulation method based on model features by combining key motion unit analysis and various simulation methods and then applied the method to the CRDM simulation process.CRDM performs motion unit decomposition through the structural hierarchy of function-movement-action method,and the key meta-actions are identified as the nodes in the flow field simulation.We established a fused feature-based multimethod simulation process and processed the simulation methods and data according to the features of the fluid domain space and the structural complexity to obtain the fusion simulation results.Compared to traditional simulation methods and real measurements,the simulation method provides advantages in terms of simulation efficiency and accuracy.展开更多
The mean wind-induced interference effects between two high-rise buildings,in which the interfering buildings have different heights,were numerical simulated in the terrain roughness of B and D types by the Reynolds s...The mean wind-induced interference effects between two high-rise buildings,in which the interfering buildings have different heights,were numerical simulated in the terrain roughness of B and D types by the Reynolds stress equation model(RSM)of fluent.The results are in good agreement with those of the wind tunnel test.Influences of the relative arrangement of two buildings,the height of the interfering buildings and the terrain roughness upon the mean interference effects were analyzed,and the space distributions of IFCPs on the principal building under tandem arrangement were studied.The results indicate that the lower interfering buildings can always bring larger interference factors comparing to the higher ones under tandem arrangement except that the height is larger than 1.25h,and the heights' influence on the mean interference effects will increase as the reduced spacing of two buildings.The influence of heights will be little under stagger arrangement.展开更多
The main structural parameters of the IR100-80-100A type chemical centrifugal pump have been optimized by means of an orthogonal test approach.The centrifugal pump has been modeled using the CFturbo software,and 16 se...The main structural parameters of the IR100-80-100A type chemical centrifugal pump have been optimized by means of an orthogonal test approach.The centrifugal pump has been modeled using the CFturbo software,and 16 sets of orthogonal-test schemes have been defined on the basis of 4 parameters,namely,the blade number,blade outlet angle,impeller outlet diameter,and impeller outlet width.Such analysis has been used to determine the influence of each index parameter on the pump working efficiency and identify a set of optimal combinations of such parameters.The internalflowfield in the centrifugal pump has been simulated by using the PumLinx software.These numerical results have shown that,compared with the prototype pump,the outlet pressure and shaft power of the optimized pump can be significantly reduced,and the pump working efficiency can be improved by 5.59%.In the present study,some arguments are also provided to demonstrate that,with respect to other optimization methods,the orthogonal test approach is more convenient,and requires less test times.展开更多
基金Thanks to Major Scientific and Technological Innovation Projects in Shandong Province(2018-CXGC0803)for the financial support of this article.
文摘Proton exchange membrane fuel cells(PEMFCs)are largely used in various applications because of their pollution-free products and high energy conversion efficiency.In order to improve the related design,in the present work a new spiral flow field with a bypass is proposed.The reaction gas enters the flow field in the central path and diffuses in two directions through the flow channel and the bypass.The bypasses are arranged incrementally.The number of bypasses and the cross-section size of the bypasses are varied parametrically while a single-cell model of the PEMFC is used.The influence of the concentration of liquid water and oxygen in the cell on the performance of different flow fields is determined by means of Computational fluid dynamics(COMSOL Multiphysics software).Results show that when the bypass number is 48 and its cross-sectional area is 0.5 mm^(2),the cell exhibits the best performances.
基金the National High Technical Reasearch and Development Programme of China (No. 2003AA327140) the National Natural Science Foundation of China (No. 50374081).
文摘Two full 3D steady mathematical models are developed by finite element method (FEM) to calcalate coupled physics fields. the electro-magnetic model is built and solved first and so is the fluid motion model with the acquired electromagnetic force as source body forces in Navier-Stokes equations. Effects caused by the ferromagnetic shell, busbar system around, and open boundary problem as well as inside induced current were considered in terms of the magnetic field. Furthermore, a new modeling method is found to set up solid models and then mesh them entirely with so-called structuralized grids, namely hex-mesh. Examples of 75kA prebaked cell with two kinds of busbar arrangements are presented. Results agree with those disclosed in the literature and confirm that the coupled simulation is valid. It is also concluded that the usage of these models facilitates the consistent analysis of the electric field to magnetic field and then flow motion to the greater extent, local distributions of current density and magnetic flux density are very much dependent on the cell structure, the steel shell is a shield to reduce the magnetic field and flow pattern is two dimensional in the main body of the metal pad.
基金financially supported by the National Science Foundation of China(Nos.51274233,51574273)the Province Natural Science Foundation(Grant No.ZR2014EEM045)。
文摘A simulation method for slug flow based on the VOF multiphase flow model was implemented in ANSYS?Fluent via a user-defined function(UDF)and applied to the dissipation of liquid slugs in the inlet pipe of a gas–liquid cylindrical cyclone(GLCC)separator while varying the expanding diameter ratio and angle of inclination.The dissipation of liquid slug in inlet pipe is analyzed under different expanding diameter ratios and inclination angles.In the inlet pipe,it is found that increasing expanding diameter ratio and inclination angle can reduce the liquid slug stability and enhancing the effect of gravity,which is beneficial to slug flow dissipation.In the cylinder,increasing the expanding diameter ratio can significantly reduce the liquid carrying depth of the gas phase but result in a slightly increase of the gas content in the liquid phase space.Moreover,increasing the inclination angle results in a decrease in the carrying depth of liquid in the vapor phase,but enhances gas–liquid mixing and increases the gas-carrying depth in the liquid phase.Taking into consideration the dual effects of slug dissipation in the inlet pipe and carrying capacity of gas/liquid spaces in the cylinder,the optimal expanding diameter ratio and inclination angle values can be determined.
文摘In order to explore the internal wind field flow characteristics of T4-72 type centrifugal fan, the three-dimensional model was established based on PRO/E software. Combined with computational fluid Dynamics Software Fluent 6.3, the standard model and SIMPLEC algorithm were used to simulate the wind field inside the fan. Analysis of the flow characteristics, velocity distributed and pressure distributed of the internal fluid model of the T4-72 centrifugal fan, combined with the theoretical formula to obtain the full pressure, power and efficiency performance parameters of the fan. The centrifugal fan performance curve is drawn. While compared with the experimental data, it is found that the internal flow disturbance is strong when the fan is running under low load condition and high load condition, which affects the performance of the fan and reduces the life of the fan. The numerical simulation results are consistent with the experimental results. The overall performance parameters of the fan are in good agreement, verifying the reliability of the simulation results;when the fan works between 1 - 1.4 times the rated flow rate, it can obtain a more stable flow field while maintaining higher efficiency, which provides a new idea for the optimization of the subsequent fan.
文摘To get fiber motion in condensing zone of compact spinning,velocity of this area is achieved by simulation,and then a bead-elastic rod fiber model is established.Based on simulation and dynamic analysis on this zone,governing equations are constructed and Runge-Kutta approach is used.Lastly,trajectories of fibers are calculated by specially designed Matlab procedure according to the principles mentioned above.Results show that fiber motions at different initial positions are different;X-axis velocity component makes fibers gathering on sides of suction slot;Y-axis airflow gets fibers gradually close and then stick to the surface of lattice apron.Fiber motions also reflect that the compact spinning process in condensing zone can be divided into three parts:fast convergence zone,adjustment convergence zone,and steady convergence zone.
基金Supported by the National Natural Science Foundation of China(No.61105086)Self-Planned Task(SKLRS-2010-MS-12)of State Key Laboratory of Robotics and System(HIT)Hubei Province Natural Science Foundation(No.2010CDB03405)
文摘In order to solve the problem of using middle or low water pressure to form fine water mist,a new nozzle is proposed in fire rescue robot.Existing water mist nozzles are basically used for high pressure and in large size,complex structure and poor low pressure atomization effect in comparison with requirement of snake-like fire rescue robots.On the basis of comprehensive typical spray nozzles,a direct spiral double helix converging nozzle(DSDHCN) is proposed,which has the advantages of small volume,light weight,simple structure,and convenient installation.To make the spray nozzle have good performance,and meet the requirements of more efficient fire extinguishing,a numerical study is carried out to analyze the internal and external full flow field of nozzle.A gas-liquid two-phase flow is applied to simulate the external full flow field of nozzle with VOF model in fluent software.The simulation results show the real situation of water flow out of the atomization nozzle and the water jet trajectory.Some simulations about middle or low water pressure direct spiral double helix converging optimized nozzle have been done in 30 bar pressure.The simulation results show that the optimized nozzle structure not only makes the spray droplets have a good cone angle,but also have a sufficient axial velocity,which proves the structure rationality of the proposed optimized nozzle.
基金supported by the National Natural Science Foundation of China (No. 52075350)the Special City School Strategic Cooperation Project of Sichuan University and Zigong (No.2021CDZG-3)
文摘The control rod drive mechanism(CRDM)is an essential part of the control and safety protection system of pressurized water reactors.Current CRDM simulations are mostly performed collectively using a single method,ignoring the influence of multiple motion units and the differences in various features among them,which strongly affect the efficiency and accuracy of the simulations.In this study,we constructed a flow field fusion simulation method based on model features by combining key motion unit analysis and various simulation methods and then applied the method to the CRDM simulation process.CRDM performs motion unit decomposition through the structural hierarchy of function-movement-action method,and the key meta-actions are identified as the nodes in the flow field simulation.We established a fused feature-based multimethod simulation process and processed the simulation methods and data according to the features of the fluid domain space and the structural complexity to obtain the fusion simulation results.Compared to traditional simulation methods and real measurements,the simulation method provides advantages in terms of simulation efficiency and accuracy.
基金the National Natural Science Foundation of China(Grant No.59895410)
文摘The mean wind-induced interference effects between two high-rise buildings,in which the interfering buildings have different heights,were numerical simulated in the terrain roughness of B and D types by the Reynolds stress equation model(RSM)of fluent.The results are in good agreement with those of the wind tunnel test.Influences of the relative arrangement of two buildings,the height of the interfering buildings and the terrain roughness upon the mean interference effects were analyzed,and the space distributions of IFCPs on the principal building under tandem arrangement were studied.The results indicate that the lower interfering buildings can always bring larger interference factors comparing to the higher ones under tandem arrangement except that the height is larger than 1.25h,and the heights' influence on the mean interference effects will increase as the reduced spacing of two buildings.The influence of heights will be little under stagger arrangement.
基金supported by the Anhui Province University Discipline(Professional)Top Talent Academic Funding Project(No.gxbjZD2021076)This project is supported by the Key Project of Natural Science Research in Colleges and Universities of Anhui Province(No.KJ2021A1026)This project is supported by the Key Project of Natural Science Foundation of Chaohu University(No.XLZ-201902).
文摘The main structural parameters of the IR100-80-100A type chemical centrifugal pump have been optimized by means of an orthogonal test approach.The centrifugal pump has been modeled using the CFturbo software,and 16 sets of orthogonal-test schemes have been defined on the basis of 4 parameters,namely,the blade number,blade outlet angle,impeller outlet diameter,and impeller outlet width.Such analysis has been used to determine the influence of each index parameter on the pump working efficiency and identify a set of optimal combinations of such parameters.The internalflowfield in the centrifugal pump has been simulated by using the PumLinx software.These numerical results have shown that,compared with the prototype pump,the outlet pressure and shaft power of the optimized pump can be significantly reduced,and the pump working efficiency can be improved by 5.59%.In the present study,some arguments are also provided to demonstrate that,with respect to other optimization methods,the orthogonal test approach is more convenient,and requires less test times.